Rare-earth metal bis(silylamide) complexes supported by ferrocene-substituted amidinate and their performance in cis-1,4 selective polymerization of isoprene

Abstract

Amine elimination of rare-earth metal tris(silylamide) complexes Ln[N(SiHMe2)2]3(THF)n (Ln = Sc, n = 1; Ln = Y, Lu, n = 2) with 1 equiv. of the ferrocene-substituted amidine FcC(NCy)NHCy (Fc = ferrocenyl, Cy = cyclohexyl) afforded the mono(amidinate) rare-earth metal bis(silylamide) complexes [FcC(NCy)2]Ln[N(SiHMe2)2]2(THF) (Ln = Sc (1), Y(2), Lu (3)). Salt metathesis reaction of anhydrous LnCl3, [FcC(NCy)2]Li(THF) and LiN(SiMe3)2 in 1:1:2 M ratio gave [FcC(NCy)2]Ln[N(SiMe3)2]2 (Ln = Sc (4), Lu (5)) as neutral derivatives. All these complexes were well-characterized by elemental analysis, NMR spectroscopy, and FI-IR spectroscopy. Complexes 1 and 3 were structurally authenticated by single crystal X-ray diffraction. In the presence of excess AliBu3, and activated by one equivalent of [Ph3C][B(C6F5)4] in toluene, all these rare-earth metal bis(silylamide) complexes could serve as catalyst precursors for cis-1,4-selective polymerization of isoprene. The ternary catalyst system of 1/[Ph3C][B(C6F5)4]/AliBu3 promoted cis-1,4 selective polymerization of isoprene in a controlled fashion.